It is generally known to mount a marker to an outside edge of an agricultural implement for forming a marked line in the ground, which is parallel to the direction of the implement's travel. The marked line then serves as references for a subsequent pass of the implement. For example, in a tractor-drawn planter that is planting a number of rows across a field, a marker attached on a structure that extends laterally outward from the side edge of the planter makes a furrow or a mark in the field that is parallel to the direction of the planter's travel and is laterally spaced from the planter. The length of the lateral spacing of the marker is related to the width of the planter so that the marker serves as a guide for alignment of the tractor on the next pass of the planter across the field to allow the planted rows to remain continuous and properly spaced to avoid overlap or other misalignment of the planted rows. Because the tractor-drawn planter can turn either to the left or to the right for the next succeeding pass across the field, markers are generally provided on both sides of the planter implement, and some sort of retraction means, preferably automatic or power-operated, is needed so that the marker on one side of the implement can be lifted or retracted while the marker on the other side is making the mark that guides the next pass.
Retraction is also necessary when transporting the agricultural implement to and from the field. In particular, folding and storing the marker assembly protects the marker from harmful, inadvertent contact with objects in the field. Toward this purpose, it is desirable that the marker assembly folds to store completely within the bounds of the agricultural implement.
With very wide planters that have foldable "wings" or outer sections, the marker must fold into a sufficiently compact form to avoid interfering with either the folding movement of the planter or the companion marker on the opposite side of the planter. This is even more important in the case of very wide implements having doubly articulated outboard sections, where first the outboard sections and then adjacent inboard sections fold up to bring the outboard sections to storage positions inboard and over the main part of the implement. Accordingly, markers intended for use on such implements must fold to a sufficiently compact position as to not interfere with the double folding action.
The folding marker assembly also must be strong enough and properly supported so as to prevent undue strain or tipping force on the outer edge of the planter during use or folding operations. In particular, the folding marker assembly cannot have too much force at the point of attachment at the outside edge of the planter. This is particularly true in the case of very wide agricultural implements that require correspondingly long markers. To address this problem, several known folding marker assemblies use a caster or support wheel partway out on the marker beam, but these elements prevent the marker assemblies from folding compactly. Accordingly, a need presently exists for a folding marker assembly that has a stable, strong structure that can fold into a compact space completely within the bounds of the agricultural implement.